Defined Benefit Pension Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	$ 561	$ 537	$ 1,683	$ 1,611
Interest cost	[2]	679	669	2,036	2,005
Expected return on plan assets	[2]	(1,318)	(1,236)	(3,954)	(3,707)
Amortization of prior service (credit) cost	[2]	(6)	(6)	(17)	(17)
Recognized net actuarial loss	[2]	374	279	1,122	836
Net periodic benefit cost		290	243	870	728
Non-Qualified Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	27	32	81	97
Interest cost	[2]	119	107	356	321
Expected return on plan assets	[2]	0	0	0	0
Amortization of prior service (credit) cost	[2]	0	0	0	0
Recognized net actuarial loss	[2]	103	76	308	269
Net periodic benefit cost		$ 249	$ 215	$ 745	$ 687

[1] Included in salaries and employee benefits expense in the Unaudited Consolidated Statements of Income.

[2] Included in other expenses in the Unaudited Consolidated Statements of Income.